The present invention relates to an injection molding apparatus for the injection molding of plastic material. The present invention particularly relates to such an apparatus including stationary and movable die carrier plates to carry respective mold parts, the movable die carrier plate being mounted to be moved in a direction toward the stationary die carrier plate during a quick stroke to close the mold parts and to be pressed toward the stationary die carrier plate during a power stroke during which injection molding within the mold parts occurs. Yet further, the present invention relates to such an apparatus wherein a single electric motor is employed to perform, through a member connected between an output of the electric motor and the movable die carrier plate, movement of the movable die carrier plate toward the stationary die carrier plate during the quick stroke to close the mold parts. However, upon changeover between the quick stroke and the power stroke, a force setting device responsive to a force acting between the output and the movable die carrier plate interrupts transmission of such movement when the force exceeds a predetermined value, and thereafter a power transmitting device connected between the output and the movable die carrier plate operates to cause further movement of the output to press the movable die carrier plate toward the stationary die carrier plate during the power stroke.
In known apparatuses of this type, i.e. employing an electric motor as a power source, for example as shown in U.S. Pat. No. 4,986,239, the changeover from the quick stroke to the power stroke occurs as soon as the movable die carrier plate has reached a desired final position. In such known arrangement however, in the event that a foreign object becomes positioned between the two mold halves, operation can be impaired.